In order to analyze a target in a specimen, a binding molecule that binds to a target is used. In addition to an antibody, a binding nucleic acid molecule that binds to a target such as an aptamer is also used as a binding molecule that binds to the target (Patent Literature 1).
As a method for obtaining the binding nucleic acid molecule, a SELEX (Systematic Evolution of Ligands by Exponential Enrichment) method in which a target is caused to come into contact with a large number of candidate polynucleotides and a polynucleotide that binds to the target among the candidate polynucleotides is selected as the binding nucleic acid molecule is known. When a binding nucleic acid molecule is obtained by the SELEX method, a modified nucleoside molecule obtained by modifying a natural nucleoside molecule is also used in addition to a natural nucleoside molecule that constitutes the binding nucleic acid molecule.
However, with known natural nucleosides and derivatives thereof, there are targets for which binding nucleic acid molecules with sufficient binding ability cannot be obtained. Therefore, there is a need for modified nucleoside derivatives that can be used, for example, in the production of aptamers.